William Wilde and the Necrosed — Davis Ashura

At seventeen years old, William Wilde was orphaned because of the magic in his veins, magic he doesn't even know exists. Eight months later, Serena Paradiso enters his life. Captivating and confident, she holds secrets about William's heritage. His friends know them, too. 

All of them watch William, studying him, wondering if he is the one for whom they've been searching. So does Kohl Obsidian, an undead horror who seeks to devour William's magic. 

William, Serena, and his friends must face Kohl together, rely on one another to defeat a creature who cannot be killed.